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Abstract Detail


Davis, Avery [1], Aguirre, Natalie [1], Nelson, Sarah [1], Borges, Adriana [1], Pierce, Emily [1], Gilderman, Gina [1], Sauer, Kaitlyn [1], Morales, Frida [1], Taylor, Mariah [1], Palmeri, Gabriella [1], Holmlund, Helen [2], Davis, Stephen Darrel [3].

Historic Drought in California Is Linked to Fungal-Induced Dieback in a Keystone Chaparral Species.

Malosma laurina (laurel sumac) is a keystone species in chaparral ecosystems of the Santa Monica Mountains in coastal, southern California. It achieves nearly 100% resprout success after periodic wildfire due to a large lignotuber and an extensive root system, including a deep taproot that extends more than 12 meters into rocky soils. Deep roots normally tap deep moisture resources during 6-9 month seasonal dry periods typical of a Mediterranean-type climate. But prolonged drought between 2013-2016 has greatly restricted access to soil moisture and is now associated with the emergence of fungal-induced dieback in the shoots of M. laurina.
We previously established that shoot dieback in M. laurina was associated with a physical blockage in xylem water transport in aboveground shoots by the fungal pathogen Botryosphaeria dothidea. We did not know if root function was also impacted. Thus we initiated a study to compare the root systems of dieback plants of M. laurina to roots of well-irrigated control plants. Our focus was on the roots’ ability to transport water to the shoot. We measured root hydraulic conductivity (Kh) and specific conductivity per unit xylem area (Ks). We found significantly lower Ks in infected plants (mean of 1.75 mg • mm-1 • s-1 • kPa-1) than in the healthy controls (4.01 mg • mm-1 • s-1 • kPa-1). We also used a double staining method that matched these functional results. Our staining procedure differentiated among vessels that were active in water transport (red stained vessels before air embolism removal), air embolized vessels (blue stained vessels after removal of air embolism), and physically blocked vessels (remained unstained by either red or blue stain).
Taken together, our results support the hypothesis that the fungus B.dothidea reduces water transport capacity not only in stems but also in roots of M. laurina, both of which likely contribute to their recent dieback. It appears that historic drought has predisposed M. laurina to fungal-induced dieback both in their shoot and root systems, and these findings indicate potential shifts in plant community structure and the decline of a keystone chaparral species. Recent adult mortality in M. laurina has already exceeded 50% in several chaparral stands of the Santa Monica Mountains. More seriously, the drought of 2013-2016 in southern California may persist with the anticipated arrival of La Nina in the Pacific Ocean.

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1 - Pepperdine University, Natural Science, 24255 Pacific Coast Highway, Malibu, CA, 90263, USA
2 - University of California, Santa Cruz, Ecology and Evolutionary Biology, 1156 High Street, Santa Cruz, CA, 95064, USA
3 - PEPPERDINE UNIVERSITY, NATURAL SCIENCE DIV, 24255 Pacific Coast Highway, MALIBU, CA, 90263-4321, USA

root hydraulics
fungal-induced dieback.

Presentation Type: Oral Paper
Session: 3, Ecophysiology
Location: 104/Savannah International Trade and Convention Center
Date: Monday, August 1st, 2016
Time: 8:00 AM
Number: 3001
Abstract ID:239
Candidate for Awards:Physiological Section Physiological Section Li-COR Prize

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